This invention relates generally to apparatus for producing tufted textile goods such as carpet, upholstery, and the like, and more particularly to a presser foot for tufting apparatus capable of producing patterned tufted goods.
U.S. Pat. No. 4,549,496 which issued Oct. 29, 1985, to Kile discloses highly advantageous tufting apparatus for producing patterned tufted goods using yarns of different colors or different textures. This apparatus is capable of placing yarn into a backing to create patterns and designs which previously were generally available only from a weaving loom or by using printing techniques. The patented apparatus employs multiple heads spaced across the width of a backing material. Each head comprises a reciprocating hollow needle or backing opener tube for penetrating the backing and for implanting yarn tufts in the backing by feeding yarn through the needle pneumatically. The needle is connected to a yarn exchanger into which a plurality of yarns of different colors, for example, are supplied, and a mechanism is included which enables the selection of one or more of the yarns for implantation into the backing for each penetration by the needle. The multiple heads are stepped in synchronism across the backing for a distance corresponding to the spacing between the heads in order to implant a transverse row of yarn tufts. The backing is then advanced to the position of the next row and the process is repeated to implant the next row. A computer controls the selection of the yarn implanted by each backing opener for each penetration of the backing in order to produce a desired pattern in the finished goods.
A significant factor influencing the production speed of practical apparatus embodying the invention of the Kile patent is the number of tufting heads embodied in the apparatus. The greater the number of heads, the less distance each head must traverse and, accordingly, the faster a row of tufts can be implanted in the backing. As the number of heads increases, however, other problems arise. The increased weight makes it more difficult to move the heads accurately and to maintain their alignment and positions relative to one another. Thus rather than the multiple heads which carry the hollow needle being moved across the backing, Ingram U.S. Pat. No. 4,991,523 discloses the backing rather than the heads being shifted transversely to move substantially less weight transversely. This not only simplifies the transverse shifting apparatus but also provides greater speed and accuracy to the yarn placement.
Additionally, the aforesaid Pat. No. 4,991,523 discloses an improved yarn cutting mechanism having significant advantages over that disclosed in the Kile patent by providing a cutting mechanism wherein a cutting blade cooperates with the backing opener tube or needle and shears the yarn as the hollow needle reciprocates into shearing engagement with the blade so that the blade acts against an angled surface forming the needle point and a slot in the angled surface holds and centers the yarn. This provides improved cutting of the yarn after it has been implanted into the backing. Moreover, the cutting apparatus includes a mechanism for permitting the yarn to be selectively cut or not cut as desired so that loop pile, cut pile, and cut/loop pile fabrics may be produced.
Another significant factor influencing the cost and accuracy of such tufting apparatus is the control over the feeding of the yarn to the hollow needle. The feeding of the yarn must be positive, and when a yarn change is to be made for a particular needle the yarn previously stitched by that needle should be positively withdrawn from the needle so that the subsequent yarn will not be blocked by the previously sewn yarn. Unless this withdrawal of the previously sewn yarn is assured, a substantially greater air pressure is required to supply the subsequent yarn through the needle. Furthermore, when the yarn is withdrawn from the needle, unless the yarn withdrawal is controlled, the next time that yarn is required to be fed to the needle an accurate and consistent length of yarn can not be assured. This would also result in requiring additional pressure to assure that a sufficient length of yarn is supplied. The effect is that a larger than required amount of pressure must be utilized, and if too much yarn is supplied to the needle additional yarn shearing operations are required for producing a satisfactory product.
This problem was solved by the apparatus disclosed in Ingram U.S. Pat. No. 625,949. There a pullback mechanism is disposed between a yarn feed roller and the hollow needle, the pullback mechanism acting to pull the yarn a preselected amount from the needle so that the yarn passageway in the needle is not restricted by the previous yarn when a subsequent yarn is to be sewn. Additionally, to assure that the pullback mechanism draws yarn from the needle and not from the yarn supply or the feed roller, clamping apparatus is disposed between the yarn feed roller and the pullback mechanism for positively clamping the yarn when a yarn change is to be made. The pullback mechanism is thereafter activated and the yarn feed roller ceases positive feeding of the yarn. Thus, the yarn pullback mechanism draws a predetermined amount of yarn from the needle maintaining it in reserve until again required. Additionally, the yarn feed roller as it ceases positive feeding draws a preselected amount of yarn from the yarn supply for immediate subsequent use when needed. When the needle is to commence stitching with a particular yarn, the yarn feed roller is activated and the yarn clamping apparatus and yarn pullback mechanism are deactivated.
A further significant factor influencing the efficiency of the aforesaid apparatus and the appearance of the product produced thereby is the disposition of the yarn on the reverse side of the backing. Because of the hollow needle, the use of air to blow the yarn to form a loop, and the slot in the angled point forming surface which acts to capture and hold the yarn for cutting, when the needle is withdrawn from a first penetration of the backing and thereafter commences to make a second penetration spaced transversely from the first penetration, the yarn strand extending from the first penetration into the hollow of the needle after withdrawal of the needle from the first penetration is initially disposed against the side wall of the hollow and thereafter on the subsequent down stroke is captured by the slot in the rear of the needle, which is 90.degree. therefrom. This results in excess yarns on the backing which forms a loop in the back stitch that stands above the surface of the backing rather than sitting flat thereon. In conventional tufting machines, for example, the looper or hook which cooperates with the needle holds the loop to pull the yarn so that the back stitch is disposed against the backing, and in conventional hollow needle tufting machines the needle does have the slot for aiding cutting of the yarn. Although this difficulty may be overcome by feeding either a greater amount of air to the needle or feeding air under a higher pressure, such a solution presents other problems such as possible unthreading of the yarn from the yarn exchanger of the apparatus. Thus, the present invention is directed toward an effective and efficient solution to this difficulty.